Determination of apoptosis and cell cycle distribution by the Nicoletti technique. PB B cells were cultured with the indicated agents for 3 days, and DNA content was determined by the Nicoletti technique as described in Materials and Methods. The percentage of apoptotic cells in the subdiploid peak is indicated by M1, and the percentage of cells in the S/G2/M phase of the cell cycle by M2. The results are from one representative experiment of three.